Voice muffler



Feb. 23, 1954 H, C, TUTTLE 2,670,054

VOICE MUFFLER Filed July 2l 1950 6 8 IIIIIIIIIIIIIIIIIII 48 40 I l Y I INVENTOR.

Patented Feb. 273, 1954 UNITED STATES PATENT OFFICE VOICE MUFFLER Harry C. Tuttle, New York, N. Y.

Application July 21, 1950, Serial No. 175,102

The present invention relates to a voice muflier, and more particularly to a voice muffler for a telephone transmitter. K

It is an object of the present invention to provide a voice muiiler which effectively operates over a range of frequencies which contribute most to the intelligibility of speech transmission by telephone, namely, those frequencies lying between 500 and 2000 cycles per second.

It is a further object of the present invention to provide a lter of the low frequencies between the mouth of the speaker and the outside atmosphere through a construction designed to attenuate these` low frequencies by the time they reach the outside atmosphere so that their audibility and intelligibility shall be negligible and in order that these low frequencies, by being allowed to escape in attenuated form, shall not have a blasting effect on the transmitter.

It is a still further object of the present inven- .u

tion to minimize the air blast caused by speech in an enclosed space so that this air blast shall have a negligible eiect on the telephone transmitter.

It is still another object'of the present invention to make possible a voice muiiier assmall as possible in cubic content so that the size and weight shall be most practical and convenient for use on the hand-set phone. The design of the present invention above referred to as respects filtering low frequencies and minimizing the air blast is essential to this end.

Another object of this invention is to accomplish the muiing of the voice while at the same time preserving the naturalness and identifying quality of the speakers voice.

The present invention comprises in its broadest aspects a casing, a highly sound-absorbent entrance wall arranged at one end of the casing and having an entrance aperture, means for attaching the casing to a telephone transmitter with the entrance wall at least partly in the path of at least part of the sound waves to be transmitted by the telephone transmitter, a sound duct arranged in the casing and leading from a location n ear the entrance wall to the rear end of the casing, and a sound-absorbent material arranged in the casing soy as to fill part of the same and to surround a portion of the duct.

In a preferred embodiment of the present invention a wire mesh is arranged at the outer side of the casing and covers at least part of the entrance wall and the aperture.

Preferably an opening is arranged in the rear portion of said casing and the duct leads to a location near the opening.

3 Claims. (Cl. 181-34) In a preferred embodiment of the present invention the duct subdivides the interior of the casing into a lower part and an upper part containing the entrance wall.

In a preferred embodiment of the present invention the sound-absorbent material includes a first portion and a second portion, the rst portion being arranged in the lower part of the casing and iilling the same except a lower portion in the rear end of the casing, the second portion being arranged in the upper part of the casing and filling the same except an upper portion in the rear end of the casing and preferably a portion arranged between the duct and the entrance wall, the rst portion and the second portion of the sound-absorbent material merging into each other so as to surround the middle portion of the duct.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. i is a sectional elevation of a voice muflicr according to the present invention; and

Figs. 2, 3 and 4 are cross-sections taken, respectively, along the lines 2-2, 3--3 and 4--4 of Fig. l.

Referring now to the drawings, the voice muer comprises a casing I0 having at one end thereof an entrance Wall I2 consisting of a highly sound-absorbent material such as cotton, wool, glass wool, fiber glass or the like. The entrance wall I 2 is provided with an entrance aperture I4 arranged approximately at the center of the entrance wall I2. A wire mesh IB is arranged at the outer side of the casing I0 and covers at least part of the entrance wall I2 and the entrance aperture I4, so as to support the material of the entrance wall. The front part I8 of the casing carries an extension 20 which is provided with an aperture in a vertical side wall 22 there- 4of for attaching the telephone transmitter 24 to the casing I0. Furthermore, the extension 20 is provided with an aperture 26 the edges of which are curved so as to form a member 28 fitting the mouth of a person using the muiiier. The extension 20 forms a chamber of substantially triangular cross-section as shown in Fig. l.

It will be understood that the entrance wall I2 is at least partly in the path of at least part of the sound waves to be transmitted by the telephone transmitter.

A sound duct 3Q is arranged in the interior of the casing i so as to subdivide the same into a lower part 32 and an upper part 3 containing the entrance wall l2. The duct 30 leads from a location near the entrance wall l2 to the rear end 35 of the casing which is subdivided by the duct 3&3 into a lower portion 3B and an upper portion lid. The upper portion 40 is provided with an opening d2 forming a connection of the interior of the casing i@ with the atmosphere.

The duct 3) is preferably constituted by a lower I wire mesh Il@ and an upper wire mesh 46 which extend substantially through the entire width of the casing lil and are connected at the mid portion of the sides thereof by narrow pieces 48 and 50 (Fig. 2) of felt or the like.

A sound-absorbent material such as cotton, wool, glass wool, ber glass or the like is arranged "in the casing Eil andincludes .a Aiirst portion 52 anda second portion 513. The lower portion 52 is arranged in the lower part 32 of the casing l and fills the same entirely except the lower portion 38 in the rear end of the casing l0'. The second portion 54 is arranged in the upper part 34 of the casing i i? and ills the same except the upper portion 4i) in the rear end of the casing i0 and -a portion arranged between the duct 30 and 'the entrance wall i2. Thev portion 56 has a tapering cross-section having its greatest width at the front portion i8 of the casing ill. The rst portion 52 and the second portion 54 of the soundabsorbent material merge into each other as shown in Fig. 2 inthe middle portion of the duct 30 so as to surround the same.

The operation of this device is yas follows: The casing iii is attached toa telephone transmitter as indicated in Fig. 1 and the person who 'wishes to use the telephone speaks into the opening 25. The sound waves coming from the mouth of the person using the device hit partly the highly sound-absorbent entrance wall l2 of the casing and part of the sound waves enter through "the entrance opening i4 and reach the portion 58 of a chamber 56 inside the casing I ii, from rwhere they enter the duct 3B leading to the rear 'portion 35 of the casing Iii.

The sound Waves entering the duct 3U are attenuated by the sound- ;absorbent material 52, 5d, and are then discharged into a chamber arranged in the rear portion 3B of the casing ill which is in communication with the atmosphere through the opening 42.

' Only a small portion of the sound entering However, the highly tortion of the voice so that a person at the other end of the telephone line can clearly recognize Iand. understand the voice of the person using f-the device.

It. will be understood that each of the elements .described above, or two or more together, may .also find a useful appplication in other types of voice muiiiers differing from the types described above.

While I have illustrated and described the invention as embodied in a voice muiiier for a telephone transmitter, I do not intend to be limited to the details shown, since various modifications nand structural changes may be made without departing in any way from the spirit of my invention.

Without further analysis, the foregoing will so fully reveal the gist of my invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What I claim as new and desire to secure by Letters Patent is z 1. A voice mufer for a telephone transmitter, comprising in combination, a casing; a highly sound-absorbent and sound-permeable entrance layer of free iibrous material arranged at one end of said casing and having an entrance aperture; a Wire mesh arranged at the outer side of said casing and covering at least part of said entrance layer and said aperture; means for attaching said casing to a telephone transmitter with said entrance layer at least partly in the path of at least part of the sound waves to be transmitted by the telephone transmitter; a sound duct arranged in said casing and leading from a location near said entrance layer to the rear end of said casing; a sound-absorbent material arranged in said casing so as to ll part of the same and to surround the middle portion of said duct; and a chamber arranged in the rear end of said casing, said chamber forming an empty space surrounding said duct and having an opening connecting said empty space to the atmosphere whereby sound waves transmitted through said duct enter said empty space from which they are discharged in attenuated form through said opening into the atmosphere.

2. A voice muiiler for a telephone transmitter, comprising in combination, a casing; a highly sound-absorbent and sound-permeable entrance layer of free brous material arranged at one end of said casing and having an entrance aperture; means for attaching said casing to a telephone transmitter with said entrance layer at least partly in the path of at least part of the sound Waves to be transmitted by the telephone transmitter; an opening arranged in the rear portion of said casing; a sound duct arranged in said casing and leading from a location near said entrance layer to a location near said opening arranged in the rear portion of said casing; a sound-absorbent material arranged in said casing so as to ll part of the same and to surround the middle portion of said duct; and a chamber ,arranged in the rear end of said casing and vforming an empty space surrounding said duct, said empty space being connected by said opening to the atmosphere whereby sound waves transmitted through said duct enter said empty space from which they are discharged in attenuated form through said opening into the atmosphere.

3. A voice muiiler for a telephone transmitter, comprising in combination, a casing; a highly sound-absorbent and sound-permeable entrance layer of free iibrous material arranged at one end of said casing and having an entrance aperture; a wire mesh arranged at the outer side of said casing and covering at least part of said entrance layer and said aperture; means for attaching said casing to a telephone transmitter with said entrance layer at least partly in the path ofatleast part of the sound waves to be Fl'aSmted by the telephone transmitter; an

opening arranged in the rear portion of said casing; a sound duct arranged in said casing so as to subdivide the interior of the same into a lower part and an upper part containing said entrance layer, said duct leading from a 1ocation near said entrance layer to the rear end of said easing; and a sound-absorbent material including a first portion and a second portion, said rst portion being arranged in said lower part oi said casing and iling the same except a lower portion in the rear end of said casing, said second portion being arranged in said upper part of said casing and lling the same except an upper portion in the rear end of said casing containing said opening, said iirst portion and said second portion of said sound-absorbent material merging into each other so as to surround the middle portion of said duct, said lower and upper 6 portions forming a chamber free of soundabsorbent material and having an opening communicating with the atmosphere, whereby sound waves transmitted through said duct enter said chamber from which they are discharged in attenuated form through said opening into the atmosphere.

HARRY C. TU'I'ILE.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,131,820 Seher Oct. 4, 1938 2,245,724 Seher June 17, 1941 2,478,783 Seher Aug. 9, 1949 2,508,581 Morrow May 23, 1950 2,566,975 Beranek Sept. 4, 1951 

